NAME
POE::Component::Client::Keepalive - manage connections, with keep-alive
SYNOPSIS
use warnings;
use strict;
use POE;
use POE::Component::Client::Keepalive;
POE::Session->create(
inline_states => {
_start => \&start,
got_conn => \&got_conn,
got_error => \&handle_error,
got_input => \&handle_input,
}
);
POE::Kernel->run();
exit;
sub start {
$_[HEAP]->{ka} = POE::Component::Client::Keepalive->new();
$_[HEAP]->{ka}->allocate(
scheme => "http",
addr => "127.0.0.1",
port => 9999,
event => "got_conn",
context => "arbitrary data (even a reference) here",
timeout => 60,
);
print "Connection is in progress.\n";
}
sub got_conn {
my ($kernel, $heap, $response) = @_[KERNEL, HEAP, ARG0];
my $conn = $response->{connection};
my $context = $response->{context};
if (defined $conn) {
if ($response->{from_cache}) {
print "Connection was established immediately.\n";
}
else {
print "Connection was established asynchronously.\n";
}
$conn->start(
InputEvent => "got_input",
ErrorEvent => "got_error",
);
return;
}
print(
"Connection could not be established: ",
"$response->{function} error $response->{error_num}: ",
"$response->{error_str}\n"
);
}
sub handle_input {
my $input = $_[ARG0];
print "$input\n";
}
sub handle_error {
my $heap = $_[HEAP];
delete $heap->{connection};
$heap->{ka}->shutdown();
}
DESCRIPTION
POE::Component::Client::Keepalive creates and manages connections for
other components. It maintains a cache of kept-alive connections for
quick reuse. It is written specifically for clients that can benefit
from kept-alive connections, such as HTTP clients. Using it for one-
shot connections would probably be silly.
new
Creates a new keepalive connection manager. A program may contain
several connection managers. Each will operate independently of the
others. None will know about the limits set in the others, so it's
possible to overrun your file descriptors for a process if you're not
careful.
new() takes up to four parameters. All of them are optional.
To limit the number of simultaneous connections to a particular host
(defined by a combination of scheme, address and port):
max_per_host => $max_simultaneous_host_connections, # defaults to 4
To limit the overall number of connections that may be open at once,
use
max_open => $maximum_open_connections, # defaults to 128
Programs are required to give connections back to the manager when
they are done. See the free() method for how that works. The con-
nection manager will keep connections alive for a period of time
before recycling them. The maximum keep-alive time may be set with
keep_alive => $seconds_to_keep_free_conns_alive, # defaults to 15
Programs may not want to wait a long time for a connection to be
established. They can set the request timeout to alter how long the
component holds a request before generating an error.
timeout => $seconds_to_process_a_request, # defaults to 120
allocate
Allocate a new connection. Allocate() will return immediately. The
allocated connection, however, will be posted back to the requesting
session. This happens even if the connection was found in the compo-
nent's keep-alive cache.
Allocate() requires five parameters and has an optional sixth.
Specify the scheme that will be used to communicate on the connection
(typically http or https). The scheme is required, but you're free
to make something up here. It's used internally to differentiate
different types of socket (e.g., ssl vs. cleartext) on the same
address and port.
scheme => $connection_scheme,
Request a connection to a particular address and port. The address
and port must be numeric. Both the address and port are required.
address => $remote_address,
port => $remote_port,
Specify an name of the event to post when an asynchronous response is
ready. This is of course required.
event => $return_event,
Set the connection timeout, in seconds. The connection manager will
post back an error message if it can't establish a connection within
the requested time. This parameter is optional. It will default to
the master timeout provided to the connection manager's constructor.
timeout => $connect_timeout,
Specify additional contextual data. The context defines the connec-
tion's purpose. It is used to maintain continuity between a call to
allocate() and an asynchronous response. A context is extremely
handy, but it's optional.
context => $context_data,
In summary:
$mgr->allocate(
scheme => "http",
address => "127.0.0.1",
port => 80,
event => "got_a_connection",
context => \%connection_context,
);
The response event ("got_a_connection" in this example) contains sev-
eral fields, passed as a list of key/value pairs. The list may be
assigned to a hash for convenience:
sub got_a_connection {
my %response = @_[ARG0..$#_];
...;
}
Four of the fields exist to echo back your data:
$response{address} = $your_request_address;
$response{context} = $your_request_context;
$response{port} = $your_request_port;
$response{scheme} = $your_request_scheme;
One field returns the connection object if the connection was suc-
cessful, or undef if there was a failure:
$response{connection} = $new_socket_handle;
On success, another field tells you whether the connection contains
all new materials. That is, whether the connection has been recycled
from the component's cache or created anew.
$response{from_cache} = $status;
The from_cache status may be "immediate" if the connection was imme-
diately available from the cache. It will be "deferred" if the con-
nection was reused, but another user had to release it first.
Finally, from_cache will be false if the connection had to be created
to satisfy allocate().
Three other fields return error information if the connection failed.
They are not present if the connection was successful.
$response{function} = $name_of_failing_function;
$response{error_num} = $! as a number;
$response{error_str} = $! as a string;
free
Free() notifies the connection manager when connections are free to
be reused. Freed connections are entered into the keep-alive pool
and may be returned by subsequent allocate() calls.
$mgr->free($socket);
For now free() is called with a socket, not a connection object.
This is usually not a problem since POE::Component::Connec-
tion::Keepalive objects call free() for you when they are destroyed.
Not calling free() will cause a program to leak connections. This is
also not generally a problem, since free() is called automatically
whenever connection objects are destroyed.
shutdown
The keep-alive pool requires connections to be active internally.
This may keep a program active even when all connections are idle.
The shutdown() method forces the connection manager to clear its
keep-alive pool, allowing a program to terminate gracefully.
$mgr->shutdown();
SEE ALSO
POE POE::Component::Connection::Keepalive
BUGS
http://rt.cpan.org/NoAuth/Bugs.html?Dist=POE-Component-Client-Keepalive
tracks the known issues with this component. You can add to them by
sending mail to bug-poe-component-client-keepalive@rt.cpan.org.
LICENSE
This distribution is copyright 2004 by Rocco Caputo. All rights are
reserved. This distribution is free software; you may redistribute it
and/or modify it under the same terms as Perl itself.
AUTHOR
Rocco Caputo
Special thanks to Rob Bloodgood.